The causal relationship between heat shock protein (HSP) and second window of cardioprotective effect is still undetermined. In the present study, we assessed whether HSP-producing substances, amphetamine and ketamine, afforded protection against reperfusion-induced ventricular fibrillation (VF) and these protective effect remained after the inhibition of HSP72 production by quercetin, a mitochondrial ATPase inhibitor. Adult mongreal male cats (n=60, 2.5∼4 kg) were used in this study. Experimental animals were divided into five groups; control group (n=15), amphetamine ('A', n=11) group, ketamine ('K', n=9) group, amphetamine-ketamine ('AK', n=16) group and amphetamine-ketamine-quercetin ('AKQ', n=9) group. Twenty-four hours after the drug treatment, an episode of 20-min coronary artery occlusion was followed by 10-min reperfusion. The incidence of reperfusion-induced VF in the AK and AKQ groups was significantly lower than that in control group (p＜0.01). After the ischemia/reperfusion procedure, western blot analysis of HSP72 expression in the myocardial tissues resected from each group was performed. HSP72 production in the AK group was marked, whereas HSP72 was not detected in the AKQ and control groups. These results suggest that the suppressive effect against reperfusion-induced VF induced by amphetamine and ketamine is not mediated by myocardial HSP72 production but by other mechanisms.